This invention relates to liquid fuel dispensing equipment for automotive service stations or the like whereby liquid fuel such as gasoline is dispensed from fuel storage reservoirs to automotive vehicles or, in some instances, to small fuel containers. The invention particularly relates to vapor recovery systems for such equipment wherein the escape of hydrocarbon vapors to the atmosphere during the refueling process is prevented by drawing the vapors back to the fuel storage reservoir through a vapor return line associated with a flexible fuel hose.
More particularly, the invention relates to a device for removing liquid fuel that may block the vapor return line, which liquid fuel results from condensation or splashback, for example.
Liquid fuel dispensing equipment conventionally includes a pump connected to a fuel reservoir, a valved nozzle adapted to be inserted into the fill pipe of a vehicle fuel tank, and a flexible fuel hose connected between the pump outlet pipe and the valve nozzle. The equipment also includes, in most cases, a vapor recovery system for preventing the escape of hydrocarbon fuel vapors to the atmosphere.
Previous vapor recovery systems have included passages in the valved nozzle for collecting vapor from the vehicle fuel tank, and a vapor return line integral with the flexible fuel hose for delivering the vapor back to the fuel storage reservoir. Some systems use a vacuum pump for drawing vapor through the return line and others rely on vapor pressure in the vehicle fuel tank for delivery of vapor through the vapor return line. Often, the return line is defined by the inner wall of an outer hose or sleeve and the outer surface of a smaller diameter flexible inner hose which constitutes the liquid fuel conduit.
The vapor return line, however, frequently becomes blocked with liquid fuel due to condensation of fuel vapors and/or splashback that occurs during the refueling operation. As a result, the vapor recovery system fails and hydrocarbon vapors escape to the atmosphere. Usually, the liquid fuel collects in the lowest portion of the flexible fuel hose, such as in the loop that commonly forms between the ends of the hose.
One solution to this liquid blockage problem is a system wherein a suction tube is positioned in the vapor return passage (i.e., the passage defined by the inner wall of the flexible outer sleeve and the outer wall of the fuel tube), with one end of the passage extending to the approximate low point in the conduit where liquid fuel collects. The other end of the suction tube extends to a suction-producing device which is integral with the nozzle.
The suction-producing device may include, for example, a venturi block connected in series with the liquid fuel conduit through which the fuel passes into the valved nozzle. The block defines a venturi throat and the other end of the suction tube is connected to a radial passage extending through the wall of the block to the venturi throat so that the pressure drop in the throat produces suction in the tube. Accordingly, the collected liquid fuel is drawn through the suction tube into the venturi throat and is dispensed through the nozzle with the normal fuel flow.
One disadvantage of this prior art device, however, is that the suction tube is vulnerable to blockage by small particles within the fuel hose. Also, backflow may occur when the flow of liquid fuel through the venturi is shut off.
Another disadvantage of the prior art device is that the restriction of the venturi throat prevents the flow of a sufficient amount of fuel through the fuel hose whereby the refueling process for an automotive vehicle fuel tank is relatively slow and time consuming. However, if the throat of the venturi is made larger, insufficient suction is produced in the venturi to aspirate the liquid fuel from the vapor return line into the throat of the venturi.
The device according to copending application Ser. No. 803,152, overcomes many of the difficulties and disadvantages described above and affords other features and advantages heretofore not obtainable.
That application provides a device which is adapted to be inserted in a liquid fuel dispensing hose of the coaxial type that includes an inner tube defining a fuel conduit and a tubular outer sleeve that defines, with the outer surface of the inner tube, a generally annular passage for removing fuel vapors from the vehicle fuel tank. The device includes a venturi section adapted for insertion in series with the inner tube within the outer sleeve. The venturi section comprises a cylindrical block defining axial connecting means at each end for connection to end portions of the inner tube. The block also defines a venturi throat communicating at opposite ends with the connected ends of the inner tube.
At least three radially extending aspirator elements are disposed in the block and extend radially through the venturi section at uniformly spaced radial locations in a transverse plane that intersects the block at approximately the throat of the venturi. Each aspirator element defines a radial port communicating between the venturi throat and the annular vapor passage. A check valve is associated with each aspirator element to block backflow of fuel from the fuel conduit whenever fuel flow is stopped. Accordingly, liquid fuel that condenses or collects in the annular vapor passage adjacent the venturi section will be sucked through at least one of the aspirator elements due to the suction generated in the venturi throat.
While the arrangement disclosed in the above-identified copending patent application overcomes many of the problems associated with the prior art vapor return systems, it has some inherent drawbacks. Since all of the liquid fuel is forced through the relatively small venturi nozzle, the available flow rates are relatively small and are not significantly increased by increasing the back pressure or by employing larger, and more expensive, fuel pumps.
It is, therefore, desired to provide an apparatus including further improvements upon the device disclosed in the above-identified copending patent application.